Production of isobutane



compound are produced.

Patented Jan. 15,1946

UNITED STATES PATENT OFFICE monuc'rron or rsonu'rana Vladimir Ipatiei! and Herman Pines, Riverside, I 11]., assignors to Universal Oil Products Company, Chicago, 111., a corporation of Delaware 7 No Drawing. Application July 19, 194:,

Serial No. 495.365

3 Claims. (01. Mil-45 83.5)

This application is a continuation-impart of I our co-pending application #434,905 flied March 16, 1942 which is a continuation-in-part of our application #103,383, filed September 30, 1936 which is now U. 8. Patent No. 2,283,142. r

This invention relates particularly to the treatment of butane of normal or straight-chain stru'c .ture.

In a more specific sense, the invention is concerned with a process whereby normal butane is converted into isobutane, the process involving the use of special catalysts and particular conditions of operation which favor the isomerization reactions so that relatively high yields of the iso- Bince the invention is concerned principally with the two 4-carbon atom paraflln hydrocarhow; and their transformation, one into the other, the following table is introduced to indicate the structurev and the principal physical characteristics of these two compounds:

Propertie s of butenes Critical Critical Name Structure B, P. teriilpueara p 0 =0 i 0 GT6 n-Butanc CHiOHiOHaOHi. +0.5 151 pr 36 i-Butanc CHOH:.- 10.5 134.5

Butanes are produced in considerable quantities in the oil refining industry. They occur in substantial amounts in natural gases (in which the normal compound usually predominates), in

refinery gases ,which are evolved from crudepetroleum storage tanks, and in the primary distillation of crudes, and they are also present in,

considerable percentages in the gases produced incidental to cracking heavy petroleum fractions for the production of gasoline. In the case of cracked gas mixtures the relative proportions of iso and normal butanes va y. but the ratio of the iso to the normal compound is as a rule considerable higher than in natural gas.

Butanes may be considered as more or less marginal compounds in respect to their desirability in ordinary gasoline, that is, a certain percentage of them is essential for suilicient vapor pressure to insure ease in starting, while an excess tends to produce vapor lock. Forthese reasons the total perecntage of i-carbon atom more amenable to cracking and dehydrogena-' tion, both with and without catalysts, than the normal compound. Considering the correspond- .ing'mono-olefins, the'normal butenes are considerably more difllcult to polymerize, either thermally'or catalytically, than iso-butene, andit is found also that the octenes representing the dimers of the isobutene are of higher antikncck value than those from n-butenes which holds also forthe 'octanes produced by hydrogenation. It is, therefore, of considerable importance at the present time toconvert as much as possible of the normal butane production into iso-butane,

and the present invention is especially concerned with a process for accomplishing this object.

In one specific embodiment the present invention comprises the treatment of normal butane for the isomermization thereof into isobutane with catalysts comprising essentially metallic halides at elevated temperatures and superatmospheric pressures.-

In a preferred embodiment the catalysts comprise essentially heavy metal chlorides and hydrogen halides. Y

We havedeter'mined that by the use of the class of catalysts mentioned, and particularly by the convenient use of considerable superatmospheric pressure normal butane may be converted into iso-butane with a yield of as high as to Evidently the use of 'superatmospheric pressures of the order of 10 to 50 atmospheres at temperatures of C. and higher, besides depressing the volatilization of granular catalysts tends also to depress numerous undesirable side reactions which would result in the formation of,

" hydrogen and low molecular weight hydrocarbons, so that the reaction proceeds more or less in one direction until an equilibrium is established.

There are several alternative catalysts which may be employed in accomplishing the present isomerization reaction and, while they may be spacing materials or a The iollowing examples are introduced used more or less interchangeably,.some are more eflective than others and it is not intended to infer that they are equivalent. Among the compounds which may be employed may be mentioned aluminum chloride, zinc chloride, iron chloride, zirconium chloride, stannic chloride, and boron fluoride. Experiments have indicated hatbest results are obtained when a minor percentage of a hydrogen halide is present in the reactions along with these compounds. Some or the com pounds may be employed either in: the dry state or in aqueous solution with suitable modifications oi operating conditions. In the case of such com-.-

pounds 'as aluminum chloride, which readily sublimes, stannlc chloride, whichboils at 114' 8., and

boron fluoride, which is normally gaseous. these I are most conveniently employed in the anhydrous condition, the hydrogen halides, such-as tor exthey are not introduced with the intention of correspondingly limiting the scope of the invention.

Example I 100 parts by weight of normal butane, parts by weight of aluminum chloride and 2 parts by weight oi'hydrogen chloride were introduced under 8 pressure of about five atmospheres into a pressure vessel, which was then rotated and heated for twelve hours at an average temperature of 150 C., the maximum pressure developed being about atmospheres. After the bomb was cooled the hydrocarbons were released and fractionated and it was tound th'at they consisted of 66.5%

ample hydrogen chloride or hydrofluoric acidgbeing separately introduced in the gaseous state.

,There will be some variations ini'the relative amounts of metal salts and hydrogen halides, used at optimum treating conditions; but the, determination of the best ratios is somewhat a matter of e peri a The process may be operated under batch or continuous conditions. Qhoosing' aluminum chloride and hydrogen chloride as example or. jointly ;;used catalytic materials, batch operationsmay be conducted byv separately adding. aluminum chlo.

ride, hydrogen chloride, and normal butane to a closed pressure contaipenaiter which the container is agitated or the cpntentsstirredmeotiso-butane-and 31.9% of normal butane. This indicates that the equilibrium under these con- :ditions' is "ccnsidera'blyin iavor o! iso-butane.

r Example I! In this operation normal butane was passed ,t rough a tubular-heating element and then into an enlarged reaction chamber, into which sublim'ed aluminum chloride and hydrogen chloride gas were introduced. A pressure of about 25--to butane chanicallywhilethe temperature and pressure are .raisedby the application of externalheattopro duce a temperature corresponding to. maximum production of the. iso-compound; This type of operationisbetter adapted tosmall Scale'p'roauction, .and, plants of considerable capacity are bcstoperatedin a continuous manner. In con-' tinuous operations the butane lmay pumped throughatubular heating element-at a given temperature and pressure within the approximate ranges' previously specified and reaction broughtabout along'the line oi il'ow. by th separate or iointiniection oi proportioned amounts of metal salts and hydrogen halides, the best 'exampleoi' this type of operation being thecombinaticn of aluminum chloride and hydrogen chloride'or-ooron fluoride and hydrogen fluoride.

In thezabsenceor moisturethere' will be sub stantially. no corrosion when using these substances. After passage through. the heating'felemerit the reactants may-be passedtoenlarged in-. .sulated chambers iorthe completion oi the desired isomerization and the total products subsequently V ,iractionated to recover catalyst andseparatethe normal and iso-butanes, afterfwhich the; normal compounds may berecycledfor further treatment.

be'conducted' bypassing normal butane mixed with a hydrogen halide -,throug h beds oi heated, granular catalyst.

which may comprise any of the solidisalts mentioned; either alone or mixed with carrying or relatively inert'charactcrl.

This type of operation is readily utilizable'finfthe (Jontinuous operations may also,

ease of such compounds as'lzinc chloride, iron chloride and stannic chloride. Treatmentofthe productsin. thesecases will involve merely the condensation ot the hydrocarbon products and the recycling oithe'hydrogen halides for further dicate in a general way the natureoifthe obtainable by the use of the process,

results stantially anhydrous P rial was placed in a 30atmospheres and atemperature 0i! 160' C. were maintained on the reaction "vessels alter-which the reactionproducts were separated and it was found that the hydrocarbons consisted of about chamber which was and the normalbutane was-preheated to a temperature 01- approximately 200"v C.-.paud passed downwardly through the contactmass under a pressure ot'approximately SO'atmospheres. lipother reaction'prod'ucts.

proximately loo-butane and 30%"normal butanewere found in the reaction products, the remaining 10% comprising lighter fixed gases and Example IV The catalytic materials'employed in this case consisted oi boron fluoride-and hydrogen fluoride.

' Normal butane was preheated to. a temperature of approximately 180' C. and passed into an insulated reaction chamber at the same time as boron reaction chamber was fluoride and hydrogen fluoride wer'einiected. The nickel-lined. as this was found to further ac lerate the isomerizationreactions. An analysi's'ot the'hydrocarbon products 62% by weight or lac-butane an I products; The character of showed that they consisted oi' approximately 32% yweight of normal butane, the'remaining'products being lighter gases and some heavier polymerized the present invention and its value. commerciall have beenshown respectively by theitoregoin'g specification and examples'introduced although the proper scope of the-invention is not limitedin exact correspondencewith thedescrlptive or numerical sections.

We claimasourinvention: f" 1 i. A process to: producing isob'utanewhich comprises subjecting normal butaneto the action to in- 1'.

or stannic chloride under conditions and in the presence of. an amount. or 'hydrocen'cfiloride such a I that isomriaation for normal butane constitutes though the principal reaction '0! the process.

2. A process for producing isobutane which comprises passing normal butane and hydrogen chloride through a. reaction zone maintained under isomerizing conditions and containing stannic chloride, said conditions and the amount of hydrogen chloride being such that isomerization of normal butane constitutes the principal reaction of the process.

3. A process for producing isobutane from normal butane which comprises adding hydrogen l0 chloride to the normal butane and mbjeoting the resultant mixture under isomerizine conditions: to

' the action of a solid catalyst comprising substan tialiy anhydrous stannic chloride, said conditions and the amount of hydrogen chloride being such that isomerization of normal butane constitutes the principal reaction of the process. 

